Radial spline impeller drive for turbochargers



Dec. 4, 1951 M. L. LAND 2,577,134

RADIAL SPLINE IMPELLER DRIVE FOR TURBOCHARGERS Filed Feb. 19, 1949 2 SHEETS-SHEET 2 Q IALIgNTOg.

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Patented Dec. 4, 1951 RADIAL SPLINE WELLER DRIVE FOR TUEBOCHABGERS Malcolm L. Land, Jeannette, Pa., assignmto Elliott Company, Jeannette, Pm, a corporation of Pennsylvania Application February 19, 1949, Serial No. 77,336

(Cl. 230-l16) 1 Claim.

This invention relates to turbochargers, and

more particularly to the mounting of the impeller on the drive shaft of a turbocharger.

- Heretofore, it has been the customary practice to rigidly mount the impeller on the drive shaft by providing the shaft and bore of the impeller with keyways for receiving keys. At the high speeds at which turbocharger impellers operate, keyways in the impeller bore weaken the impeller and will cause it to burst at a much lower speed than if it had a smooth or uninterrupted bore, especially when the impeller is made of aluminum. At high turbocharger speeds the impeller tends to expand. When the impeller is provided with a key-way, this expansion will throw the impeller out of balance because it no longer will remain concentric with the shaft.

It is among the objects of this invention to provide a turbocharger in which the impeller is not weakened by keyways, and in which the impeller remains concentric with its supporting drive shaft at all speeds.

In accordance with this invention, a nosepiece is rigidly mounted on one end of the drive shaft for a turbocharger impeller. Preferably, the drive shaft is hollow and the nosepiece is held on the shaft by a nut threaded on the projecting end of a rod which extends through the shaft and holds the turbine wheel on the other end of the shaft. Also mounted on the shaft is an impeller which is provided with a smooth axial bore that snugly receives the shaft. The impeller engages the inner end of the nosepiece and is driven from the shaft through the nosepiece by means of interengaging radial splines with which the adjoining ends of the nosepiece and impeller are provided. Preferably, each spline has parallel side walls and is an integral part of one of the members that it connects. The opposite end of the impeller and an adjoining collar also may be provided with similar interengaging radial splines to help keep the impeller centered on the drive shaft at all speeds.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which Fig. 1 is a fragmentary vertical section through a turbocharger; Fig. 2 is an enlarged view of the outer end of the impeller, taken on the line 11-11 of Fig. 1; Fig. 3 is an enlarged view of the inner end of the nosepiece taken on the line III-III of Fig. 1; Fig. 4 is a fragmentary enlarged plan view of the impeller-nosepiece connection, taken on the line IV-IV of Fig.

1; and Figs. 5 and 6 are fragmentary sectional and plan views, respectively, of a modified splined connection.

Referring to Fig. 1 of the drawings, a turbocharger casing I is provided with bearings 2 through which an overhung drive shaft 3 extends. The shaft is hollow and has a rod 4 extending through it. The projecting inner end of the shaft is screwed into a turbine wheel 6 that is driven by exhaust gas from the engine (not shown) to which the turbocharger is connected. The wheel drives the shaft through pins I connecting them. The outer end of the shaft projects a considerable distance from the adjacent bearing and supports an impeller 8 provided with a smooth axial bore 9 through which the shaft extends. By smoo is meant a bore whose wall is circular in cross section and not interrupted by any longitudinally extending indentations, such as keyways, that might cause local stresses in the impeller and failure. The

shaft fits snugly in at least the opposite ends of the bore.

The inner end of the impeller engages a collar l I whose inner surface likewise is smooth so that the collar could be rotated on the shaft if that were desired. Inward movement of the collar is limited by a radial shoulder 12 with which the shaft is provided. The impeller is pressed against the collar by means of a generally coni-' cal nosepiece l3 mounted on the outer end of hollow shaft 3. The nosepiece is forced against the impeller by a washer 'H and a nut 15 on the projecting end of rod 4. When the nut is screwed up tightly on the rod it not only holds the impeller in place, but it also causes the rod to pull the turbine wheel tightly against the inner end of the drive shaft.

It is a feature of this invention that the impeller is driven from hollow shaft 3 by means of the nosepiece, rather than directly from the shaft by some connection in the axial bore of the impeller. Accordingly, the nosepiece I3 is provided with a keyway II in which thereis a key l8 that also extends into a keyway I! in the shaft. The nosepiece therefore must rotate with the drive shaft. To transmit rotation from the nosepiece to the impeller, their adjoining ends are provided with interengaging radial splines. These may be in the form of teeth on either member which project into slots in the other member. Thus, the outer end of the impeller can be provided with radial teeth 2| spaced equal distances around the shaft and projecting into corresponding radial slots 22 in the inner end of the nosepiece, as shown in Figs. 1 to 4. The radial splines also assure concentricity of the impeller on the shaft at all speeds.

The side edges of the teeth are chamfered to accommodate the fillets in the slots, and the side edges of the slots are chamfered to fit over the fillets at the base of the tongues. It is preferred that the side walls of each tongue and of each slot be parallel, or at least be parallel to a line midway between them extending radially of the shaft even though the tongues and slots are tapered in a direction lengthwise of the shaft. On the other hand, if the teeth and slots have radial side walls, the teeth always should be on the impellers so that when the impeller expands radially at high speeds the teeth will remain tight in the slots. If reversed, it would be the slots that would become slightly wider and thus loose on the teeth.

In some cases it may be desirable to also balance the inner end of the impeller on the shaft in the same way. That can be done by providing that end of the impeller and the adjoining collar with interengaging radial splines. Thus, the impeller may be provided with radial teeth 23 that project into radial slots 24 in the collar. The

collar is not and need not be keyed to the shaft, so there is no problem of lining up longitudinally spaced keyways in the shaft.

The radial splines do not have to be integral parts of the members they connect, but may, if desired, include separate keys that are inserted in registering radial slots. This embodiment of the invention is illustrated in Figs. 5 and 6 of the drawings, where it will be seen that the impeller 26 is provided with radial slots 21 that register with radial slots 28 in the nosepiece 29. As in the first form of the invention, the nosepiece is driven from the hollow drive shaft 3 by a key l8. Rotation is transmitted from the nosepiece to the adjoining end of the impeller behind it through radial splines or keys 30 that are inserted in the pairs of registering radial slots. The keys are retained in the slots in any suitable manner, such as by spot welding their outer ends to the nosepiece, which is steel.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claim, the invention may be practiced otherwise than as specifically illustrated anddescribed.

I claim:

A turbocharger comprising a hollow drive shaft, bearings supporting the shaft with its ends projecting therefrom, a rod extending through the shaft and projecting from it, a turbine wheel held on one end of the shaft by means of one end of the rod, the opposite end of the rod being threaded, an annular nosepiece keyed on the shaft adjacent said threaded end, means screwed on said threaded end 01' the rod holding the shaft under tension and the nosepiece on the shaft, an impeller between the nosepiece and the adjacent bearing and provided with a smooth axial bore through which the shaft extends, the adjoining ends of the nosepiece and impeller being provided with at least three circumferentially spaced interengaging radial splines spaced substantially uniformly around the shaft, and a collar mounted on the shaft between the opposite end of the impeller and the adjacent bearing, the adjoining ends of the collar and impeller being provided with at least three circumferentially spaced interengaging radial splines spaced substantially uniformly around the shaft, and the shaft having an annular shoulder holding the collar against the impeller, all of said splines serving to hold the impeller centered on the shaft when the impeller bore is expanded by centrifugal force.

MALCOLM L. LAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,922,929 Chamberlain Aug. 15, 1933 2,010,525 McI-Iugh Aug. 6, 1935 2,377,740 Alford June 5, 1945 2,438,866 Rockwell et a1. Mar. 30, 1948 2,483,616 Bergstedt Oct. 4, 1949 2,487,532 Eastman Nov. 8, 1949 2,556,020 Williams June 5, 1951 FOREIGN PATENTS Number Country Date 90,860 Sweden Nov. 23, 1937 

